A RAT TRANSVERSE RECTUS-ABDOMINIS MUSCULOCUTANEOUS FLAP MODEL - EFFECTS OF PHARMACOLOGICAL MANIPULATION

A study was designed to attempt to develop an experimental animal mode l for the transverse rectus abdominis musculocotaneous (TRAM) flap. Th e rat has a well-formed superior epigastric artery with musculocutaneo us perforators that have been shown to support a musculocutaneous flap on a single superior pedicle. Despite the anatomical differences betw een the dominance of the axial longitudinal cutaneous circulation in l oose-skinned animals compared with humans, as well as a dominant super ior intramuscular pedicle, the rat TRAM model appears to be reproducib le and has predictable zones of viability as well as areas that typica lly do not survive when based on a single superior pedicle. These area s of nonviability correspond to those zones at high risk of nonviabili ty in the human clinical situation: zone 3 and 4 on the contralateral side and zone 3 on the ipsilateral side (tissue lateral to the superfi cial inferior epigastric supply). Once the reliability and reproducibi lity of this model was demonstrated (coefficient of variation 18.9%), a study was undertaken to determine whether pharmacological manipulati on of this flap altered survival in those areas that are inadequately perfused. The two agents tested were allopurinol (xanthine oxidase inh ibitor, antioxidant) and pentoxifylline (microcirculatory theological agent that is a xanthine analogue and is also believed to have antioxi dant potential). The study involved creating right unipedicled TRAM fl aps in 30 male specific pathogen-free Sprague-Dawley rats weighing 375 to 450 gm. The transverse skin paddle was centered over the umbilical dimple and measured 5.5 x 2 cm. Postoperatively, they were put into e ither a control group receiving tap water ad libitum, a test group rec eiving water containing allopurinol, or a test group receiving water c ontaining pentoxifylline (Trental). Supplementation of the water in th e test groups was initiated the morning of surgery and continued until flap viability was assessed 48 hours postoperatively. There were 10 r ats in each of the groups. Results showed significantly improved flap survival in those rats receiving allopurinol compared with control rat s (p = 0.018). Mean flap survival was improved by pentoxifylline (701 mm(2)) compared with controls (590 mm(2)), but this did not reach sign ificance (p = 0.053). We believe that this rat model provides an inexp ensive, reliable, and reproducible model for musculocutaneous flap res earch to assess the effects of pharmacological manipulation.